Board of Education watchdogs will probe 170 schools today as part of a campaign to prevent cheating on high-stakes reading tests.

“Please let’s focus on real achievement and send the message that cheating will not be tolerated,” interim Schools Chancellor Harold Levy said in a memo to all superintendents and principals.

“Any incident of cheating can call into question all student achievement data and undermine the integrity of your hard work and accomplishments.”

Reading tests are being given to some 300,000 students in the third, fifth, sixth and seventh grades. Under a new promotion policy, students who fail must attend summer school – or be held back.

Investigators will visit all elementary and middle schools to curb “teacher-assisted test cheating.”

But 170 schools, including those with a history of proven or suspected cheating, will undergo additional scrutiny, said Levy deputy Burton Sacks.

Schools with an “excessive number of erasures changing responses from wrong to right” are on the hit list, too, he added.

Investigators will monitor schools in District 19 and 23 in Brooklyn. Under a special school-based merit-pay program, teachers at these schools are being offered salary bonuses for improved scores.

Investigators want to make sure the desire for higher test scores does not tempt instructors to aid or condone cheating.

Unannounced visits also will be made at random to other schools.

The snoops will arrive at 7:30 a.m. and stay for the duration of the tests.

Afterward, the Division of Assessment and Accountability will conduct audits to determine whether results for particular classes differ dramatically from citywide results and whether increases in test scores are sustained over time.

Officials also will check whether tests are being given to all eligible students.

Levy warned that that Special Schools Investigator Ed Stancik continues to probe reports of test cheating.